This invention relates to a modified melanin soluble in an organic solvent and water.
Melanin is a black dye existing in skins, eyes, hairs and feathers of animals, ink of the Cephalopoda, and fruits and seeds of plants.
Melanin is insoluble in water and almost all organic solvents, and also insoluble in acids other than hot concentrated sulfuric acid.
Thus, if melanin can be solubilized in water or an organic solvent, it will be utilized easily and can be applied variously. For example, such melanin is expected to be used as a hair dye or a dye by utilizing it as a black dye, an anti-suntan cosmetic and an ultraviolet-screening material of home and vehicular windowpanes by utilizing its effect of absorbing UV rays, and a medicine for rheumatism by utilizing its action of making peroxide non-toxic.
T.G. Bonner et al. found that an amino group existed in melanin by measuring infrared spectroscopic spectra of various melanins (Infra-Red Spectra of Some Melanins, NATURE, Vol. 194, 1078, (1962)). The present inventors also quantitated an amino group according to the trinitrobenzenesulfonate (TNBS) method in addition to measurement of infrared spectra of isolated melanins, and proved that about 8 amino groups existed in one molecule of melanin (calculated as molecular weight of melanin:14,000).